Rudder arrangement for ships having higher speeds comprising a cavitation-reducing twisted, in particular balanced rudder

ABSTRACT

The rudder arrangement for ships comprises a twisted balanced rudder blade having a slender profile and having a low profile thickness and comprising a propeller facing the rudder blade and a rudder pipe located in the upper region of the rudder blade with rudder post located therein, wherein the rudder blade comprises two superposed rudder blade sections having different heights whose front nose strips facing the propeller are offset in such a manner that one nose strip is offset to port or starboard and the other nose strip is offset to starboard or port, wherein the two side wall surfaces of the rudder blade converge into an end strip facing away from the propeller and have different arc profiles.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a rudder arrangement for ships travelling athigh speeds having a cavitation-reducing twisted, in particular balancedrudder, with a rudder blade with a propeller (115) arranged on adrivable propeller axis (PA), which is associated with the rudder blade,and a rudder post (140) connected to the rudder blade (100).

2. Description of the Related Art

Ships' rudders such as balanced rudders or balanced profile rudders,with or without a linked fin are known in various embodiments. Alsoknown are ships' rudders having a twisted rudder blade consisting of twosuperposed rudder blade sections, whose nose strips facing the propellerare laterally offset in such a manner that one nose strip is offset toport and the other nose strip is offset to starboard.

Thus, JP(A) Sho 58-30896 describes a rudder for ships having a twistedrudder blade consisting of an upper and a lower part, wherein both partsare twisted in their directions facing the propeller and specifically insuch a manner that only the regions of the two parts relating to thenose strips are laterally offset whereas the regions extending to theend strips of the two parts have the same cross-sectional profiles andthe same cross-sectional dimensions.

GB 332,082 likewise discloses a ships' rudder having a twisted rudderblade whose profile regions facing the propeller, namely the nose stripsto starboard and port are laterally flared, the nose strips beingconfigured to taper to a tip. The cross-sectional profiles of the tworudder blade sections are configured so that the side wall surfaces ofthe two rudder blade sections located on the port and starboard side runfree from curvature and rectilinearly between the end strips as far asthe laterally bent nose strips so that the side wall surfaces have nooutwardly curved regions having different radii of curvature. Inaddition, the profile configuration of the rudder blade is such that thetwo cross-sectional surfaces of the two rudder blade surfaces locatedone above the other are the same size and extend over the entire heightof the rudder blade. Due to the nose strips tapering to a peak,sharp-edged indentations are formed, which are exposed to cavitation anddestruction. An improvement in the propulsion should be achieved withthe profile configuration of this rudder.

The speeds of modern ships are continually increasing. As a result ofthe fast flow velocities associated with the higher speed, the loadingon the propeller and on the rudder is increasing. The symmetry of theprofile of known rudder blades leads to underpressure zones on therudder surface which lead to cavitations and thus to erosion. Cavitationtakes place on those points of the rudder blade at which the flow isextremely accelerated. In this case, the strong rotational flow of thepropeller impacts on the rudder blade surface at high speed. As a resultof this strong acceleration, the static pressure drops below the vapourpressure of the water, resulting in the formation of vapour bubbleswhich abruptly implode. These implosions lead to destruction of therudder blade surface, which result in expensive repairs; frequently newrudder blades must be used.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a rudderarrangement for ships having large and very large dimensions, inparticular balanced rudder blades having a twisted rudder leading edge,in which erosion effects on the rudder blade due to cavitationformation, in particular when used in fast ships having highly loadedpropellers, can be avoided and a rudder post mounting is provided inwhich the rudder pipe drawn into the rudder blade leads the rudderforces directly into the ships' hull via a collar bearing integrated atthe bottom, wherein the introduction of forces as a cantilever takesplace as pure bending stress without any torsional moments. In addition,the forces acting on the rudder blade in its lower region generated bythe propeller current having very high flow velocities, should beintercepted and the rudder blade balanced out without any damageoccurring to the bearing for the rudder post.

This object is achieved in a rudder arrangement according to the typedescribed initially as a result of the functional cooperation of atwisted balanced rudder blade with a special rudder post mounting havingthe following features.

According to the invention, the rudder arrangement

a.) consists of a balanced rudder blade preferably having a slenderprofile with a small profile thickness, comprising two superposed rudderblade sections having the same or different heights, preferablycomprising a lower rudder blade section having a smaller height comparedwith the height of the upper rudder blade section and comprising nosestrips facing the propeller, having an approximately semicircularprofile, which are positioned in such a manner that one nose strip isoffset to port BB or starboard SB and the other nose strip is laterallyoffset to starboard SB or port BB with respect to the longitudinalcentral line LML of the rudder blade, wherein the side wall surfaces ofthe two rudder blade sections converge into an end strip facing awayfrom the propeller,a1.) wherein the two nose strips and the end strip run downwards in aconically tapering manner accompanied by a reduction in thecross-sectional areas from the upper region OB to the lower region UB ofthe rudder blade,a2.) or the end strip runs rectilinearly and parallel to the rudder postand the two nose strips run downwards in a conically tapering manneraccompanied by a reduction in the cross-sectional areas from the upperregion OB to the lower region UB,a3.) wherein the cross-sectional surface sections of the upper rudderblade section and the lower rudder blade section in the region betweenthe end strip and the greatest profile thickness PD of the rudder bladehave a length L, which corresponds to at least 1½ times the length L1 ofthe cross-sectional surface sections of the upper rudder blade sectionand the lower rudder blade section between the greatest profilethickness PD of the rudder blade and the nose strips,a4.) wherein the upper rudder blade section on the port side BB and thelower rudder blade section on the starboard side SB each comprise a sidewall section running in a flat arcuate manner and extending from thenose strips in the direction of the end strip, having a length L2 whichextends over the length L′2 of the side wall sections from the nosestrips as far as the greatest profile thickness PD plus a length L″2which corresponds to at least ⅓ of the length L′2, wherein the side wallsection running in a flat arcuate manner is adjoined by therectilinearly running side wall section which runs out in the end strip,a5.) wherein the upper rudder blade section on the port side BB and thelower rudder blade section on the starboard side SB each comprise ahighly curved side wall section running in an arcuate manner andextending from the nose strips in the direction of the end strip, havinga length L3 which extends over the length L′3 of the side wall sectionsfrom the nose strips as far as the greatest profile thickness PD plus alength L″3 which corresponds to at least ⅓ of the length L′3, whereinthe highly curved side wall section running in an arcuate manner isadjoined by the rectilinearly running side wall section which runs outin the end strip,a6.) wherein the two rectilinearly running side wall sections have thesame lengths in pairs and the cross-sectional surface sections locatedbetween the two side wall sections are the same size and are configuredsymmetrically anda7.) wherein the distance between the side wall section running in aflat arcuate manner from the longitudinal central line LML is greaterthan the distance between the highly arcuately running side wall sectionfrom the longitudinal central line LML and the cross-sectional surfacesections located between the two side wall sections running in a flatarcuate manner on both sides of the longitudinal central line LML areconfigured asymmetrically andb.) consists of a rudder post cooperating functionally with the rudderblade, having at least one bearing,b1.) wherein the rudder post, in particular made of forged steel oranother suitable material, together with the rudder pipe receiving saidpost, in particular made of forged steel or another suitable material isarranged in the area of the greatest profile thickness PD or betweenthis and the nose strips of the upper rudder blade section therein andextends with its end fastening device over the entire height of theupper rudder blade section,b2.) wherein the rudder pipe for the rudder post which is drawn deeplyinto the upper rudder blade section as a cantilever is provided with acentral longitudinal hole for receiving the rudder post,b3.) wherein the rudder pipe cross-section is designed as thin-walledand the rudder pipe preferably has a collar bearing on the inner wallside in the area of its free end for mounting the rudder post, andb4.) wherein in its end region the rudder post is and the end of thissection is connected to the upper rudder blade section.

It has surprisingly been found that as a result of the configuration ofthe twisted rudder blade as a balanced rudder according to theinvention, having a small profile thickness and the mounting of therudder post in the area of the greatest profile thickness in the upperrudder blade section of the rudder blade, the lower rudder blade sectionacquires a narrow profile so that despite the high speeds of thepropeller current impinging upon the rudder blade, a balancing of therudder blade is possible without additional expenditure of force evenwhen this has the largest dimensions, which is only attainable as aresult of the functional cooperation of twisted rudder blade with therudder blade mounting but which cannot be achieved with other rudderblade configurations and rudder post mountings.

The invention provides a rudder arrangement, i.e. a system comprisingtwo components, i.e. a twisted rudder blade and a specially mountedrudder post cooperating functionally therewith. This rudder arrangementis the technical solution which has surprisingly been found for buildinglarge and extremely large balanced rudder blades. The rudder pipe drawndeeply into the upper rudder blade section of the rudder blade guidesthe rudder forces directly into the ship's hull by means of a collarbearing integrated in the lower region of the upper rudder bladesection. The forces are introduced as a cantilever, i.e. as pure bendingstressing without torsional moments. As a result, the rudder pipecross-section can be designed a relatively thin-walled. This thin-walledproperty is very important since the lower part of the rudder pipe isaccommodated in the rudder blade, i.e., in the upper rudder bladesection and thus has a direct influence on the profile thickness of therudder blade. Only a slender rudder profile, i.e. a small profilethickness makes it possible to build energy-efficient rudder bladessince the thicker the rudder profile, the more resistance it produces inthe accelerated flow of the propeller water.

A further advantage of the rudder arrangement of the combination of thetwisted rudder blade with the mounting of the rudder post is the use ofhigher-quality materials. High-strength forged steel can be used only asa result of the mounting of the rudder post in the upper rudder bladesection according to the invention so that a substantial reduction inweight is possible and is also achieved, i.e. up to 50% of theconventional rudder having the same performance.

A further substantial advantage of the rudder arrangement with thecombination of rudder post mounting is that as a result of this type ofintegrated mounting in the rudder blade, i.e. in the upper rudder bladesection, the design of the balanced rudder or spade rudder is madepossible for the first time and this in almost unlimited size.Conventional rudders are semibalanced rudders with a rudder horn orrudder support. Such intricate mechanical structures can barely betwisted at the leading edge since the fixed rudder horn and the rudderblade rotating therearound are not so freely formable. The rudder-bladeinternal forces and moments occurring in these semibalanced rudders arenon-uniformly greater than in balanced rudders having the mounting ofthe rudder post according to the invention. A significant twisting ofthe leading edge of the rudder blade facing the propeller would meanconsiderable constructively uneconomical measures, i.e. withcorrespondingly thicker profiles.

Another advantage is that due to the mounting of the rudder post,balanced rudders as a structural form are possible for the first timewhich means that gaps no longer exist between the previously requiredrudder horns and their rudder blades. As a result, transverse flowthrough these gaps is avoided and the severe cavitation erosionpertaining thereto is also avoided.

In addition, in the embodiment of the rudder arrangement according tothe invention, the rudder pipe preferably consisting of forged steel isextended into the rudder blade i.e. into the upper rudder blade sectionbut only with one lower collar bearing. The rudder post, likewise with aforged piece as hub is connected close to the hydrodynamic centre to therudder with the result that only a small loading due to bending momentsis achieved. Superposed vibrations can be eliminated by thisconfiguration.

As a result of the slender rudder profile and therefore due to the smallprofile thickness of the rudder blade, it is possible, withoutparticular stressing of the bearing for the rudder post, to balanced outthe rudder blade with respect to the high pressure of the propellercurrent impinging on the lower rudder blade section at very high speed.

In order to eliminate the cavitation at the rudder blade, this has theprofile according to the invention which is divided into an upper and alower half, whose nose strips or leading edges are twisted at certainangles. The propeller wake flow and the angle of said flow to the midship line prescribes by how many degrees the profile leading edge istwisted. As a result of this new profile variant, the propeller vortexflow flows better along the rudder blade and no pressure peaks whichpromote cavitation are formed on the profile surface of the rudderblade. The improved flow around the rudder leads to appreciable savingsof fuel and to improved manoeuvrability.

The invention thus provides a rudder blade arrangement such that afastening plate is arranged between the upper rudder blade section andthe lower rudder blade section and is firmly connected to the rudderblade sections, wherein the fastening plate has symmetricalcross-sectional surface sections on both sides of the longitudinalcentral line LML and a surface profile and dimensions which enclose thebase plate of the upper rudder blade section and the cover plate of thelower rudder blade section with their profiles and dimensions.

A further embodiment of the invention provides that the nose strip ofthe upper rudder blade section and the nose strip of the lower rudderblade section are laterally offset to port BB and starboard SB withrespect to the longitudinal central line LML in such a manner that thecentral line M2 drawn through the laterally offset nose strip sectionsis running at an angle α of at least 3° to 10° but also higher,preferably 8° to the longitudinal central line LML of thecross-sectional area of a rib.

Furthermore, an embodiment according to the invention is provided whichconsists in that the flatly curved arcuate side wall sections of theupper and lower rudder blade sections located on the port side BB andthe starboard side SB have a shorter length L4 compared with the lengthL5 of the highly curved arcuate side wall sections of the upper andlower rudder blade sections located on the starboard side SB and on theport side BB.

The invention furthermore provides that the arc length BL1 of the highlycurved arcuate side wall sections of the upper and lower rudder bladesections is far greater than the arc length (BL) of the flatly curvedarcuate side wall sections of the upper and lower rudder blade sectionsso that the transition zones ÜB1 of the highly curved arcuate side wallsections of the upper and lower rudder blade sections to the side wallsections running rectilinearly to the end strip and the transition zonesÜB of the flatly curved arcuate side wall sections of the upper andlower rudder blade sections to the side wall sections runningrectilinearly to the end strip are offset in the direction of the endstrip.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of the disclosure. For a better understanding of the invention, itsoperating advantages, specific objects attained by its use, referenceshould be had to the drawing and descriptive matter in which there areillustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the Drawing

FIG. 1 is a side view of the rudder arrangement comprising a twistedbalanced rudder blade having an upper and a lower rudder blade sectionand comprising a rudder post mounted in the upper rudder blade section,

FIG. 2 is a diagrammatic view of the twisted rudder blade of the rudderarrangement,

FIG. 3 shows a schematic skeletal diagram of the twisted rudder bladewith the outer skin removed and a number of plate-shaped frames in thetwo rudder blade sections,

FIGS. 4, 4A, 4B, 4C show four plate-shaped frames of the upper rudderblade section of the rudder blade according to FIG. 3,

FIG. 4D is an enlarged view of a plate-shaped frame of the lower rudderblade section of the rudder blade according to FIG. 3,

FIG. 4E shows a plate-shaped frame of the lower rudder blade section ofthe rudder blade according to FIG. 3,

FIG. 5 shows an enlarged reproduction of the plate-shaped frameaccording to FIG. 4,

FIG. 6 shows an enlarged reproduction of the plate-shaped frameaccording to FIG. 4, with information on the distances of the lateraledge regions from the longitudinal central line of the frame,

FIG. 7 shows a skeletal diagram of another embodiment of the twistedbalanced rudder blade comprising a plurality of plate-shaped framesarranged in the upper rudder blade section and in the lower rudder bladesection,

FIGS. 8, 8A, 8B, 8C are enlarged views from above of four plate-shapedframes of the upper rudder blade section of the rudder blade accordingto FIG. 7 with gaps for receiving the rudder pipe for the rudder post,

FIGS. 8D, 8E, 8F show enlarged views from above of three plate-shapedframes of the lower rudder blade section of the rudder blade accordingto FIG. 7,

FIG. 9 is an enlarged view from above of the cover plate of the upperrudder blade section of the rudder blade according to FIG. 7 with thegap for receiving the rudder pipe for the rudder post,

FIG. 10 is an enlarged view from below of the twisted rudder blade ofthe rudder arrangement according to FIG. 7,

FIG. 11 is an enlarged view from above of a fastening plate arrangedbetween the upper rudder blade section and the lower rudder bladesection of the rudder arrangement according to FIG. 7 having a profileand having dimensions which include the profiles and dimensions of thebase plate of the upper rudder blade section and the cover plate of thelower rudder blade section,

FIG. 12 is a front view of the twisted rudder blade,

FIG. 13 is a side view of the rudder blade with obliquely running rudderblade edges on the propeller side,

FIG. 14 is a view from above of the cross-sectional profile of a frameof the upper rudder blade of another embodiment, and

FIG. 15 is a perpendicular section of the rudder post mounting with therudder pipe for the rudder post arranged in the upper rudder bladesection.

DETAILED DESCRIPTION OF THE INVENTION

The rudder arrangement 200 according to the invention consists of twofunctionally cooperating components which achieve the object of theinvention, i.e. a preferably balanced rudder having a twisted rudderblade 100 and a rudder post 140 mounted in its upper region (FIGS. 1, 2,3, 7 and 14).

In the rudder arrangement 200 shown in FIG. 1, 110 designates a ships'hull, 120 designates a rudder pipe for receiving the rudder post 140 and100 designates the rudder blade. A propeller 115 is assigned to therudder blade 100. The propeller axis is designated by PA.

The rudder blade 100 according to FIGS. 1, 2, 3 and 7 consists of twosuperposed rudder blade sections 10, 20 whose nose strips 11, 21 facingthe propeller 115 are offset in such a manner that the nose strip 11 ofthe upper rudder blade section 10 is offset to port BB and the nosestrip 21 of the lower rudder blade section 20 is offset to starboard SBlaterally to the longitudinal central line LML of the rudder blade 100(FIGS. 4, 4A, 4B, 4C, 4D, 4E and 13). The lateral offset of the nosestrips 11, 21 can be achieved such that the nose strip 11 of the upperrudder blade section 10 is offset to starboard SB and the nose strip 21of the lower rudder blade section 20 is offset to port BB. The two sidewall surfaces 12, 13 of the upper rudder blade section 10 and the sidewall surfaces 21, 23 of the lower rudder blade section 20 run from thenose strips 11, 21 in an arcuate manner in the direction of an end strip15 facing away from the propeller 115 with interposed rectilinearlyrunning side wall sections 16, 17 and 26, 27 which open into the endstrip 15. The two rudder blade sections 10, 20 have a common end strip15 whereas each rudder blade section 10, 20 has a nose strip 11 and 21whereby the twisting is achieved as result of their lateraldisplacements.

The rudder arrangement 200 preferably comprises a balanced rudderalthough differently configured rudders can also be used if these aresuitable for fitting with twisted rudder blades and the advantages ofthe rudder blade configuration according to the invention are achieved.The two superposed rudder blade sections 10, 20 have the same ordifferent heights. The lower rudder blade section 20 preferably has asmall height compared with the height of the upper rudder blade section,the height of the upper rudder blade section 10 corresponding to atleast 1½ times the height of the lower rudder blade section 20. The nosestrips 11, 21 of the two rudder blade sections 10, 20 are configured assemicircular-arc-shaped.

The rudder blade 100 has conically downwardly running nose strips 11, 21whereas the end strip 15 is rectilinear and runs parallel to the rudderpost 140 (FIGS. 1, 2 and 3). The conical profile of the nose strips 11,21 of the two rudder blade sections 10, 20 is such that the size of thecross-sectional surfaces 30 of the two rudder blade sections 10, 20 forthe same profile configuration of the upper rudder blade section 10 andfor the same profile configuration of the lower rudder blade section 20decreases from the upper region OB to the lower region UB of the rudderblade 100 so that due to the reduction of the cross-sectional surfaces30, a downwardly extending slender profile having a small profilethickness which is in particular [determined] by the profile of the sidewall surfaces 12, 13 and 22, 23 of the two rudder blade sections 10, 20is obtained. The small profile thickness of the rudder blade 100 is alsoan essential feature of the invention.

As shown in FIG. 13, the edge or nose strip 11, 21 of the rudder blade100 facing the propeller 115 runs obliquely to the edge or end strip 15facing away from the propeller at an angle f of at least 5°, preferably10°.

The lengths L, L1 of the cross-sectional surface sections 31, 32 of bothrudder blade sections 10, 20 on both sides of the largest profilethickness PD are differently configured. The cross-sectional sections 31of the upper rudder blade section 20 and the lower rudder blade section20 in the area between the end strip 15 and the largest profilethickness PD of the rudder blade 100 have a greater length L comparedwith the length L1 of the cross-sectional surface sections 32 of theupper rudder blade section 10 and the lower rudder blade section 20between the largest profile thickness PD of the rudder blade 100 and thenose strips 11, 21. In this case, the length ratio is preferably 1½times the length L compared with the length L1 (FIG. 5).

The configuration of the rudder blade is such that the upper rudderblade section 10 on the port side BB and the lower rudder blade section20 on the starboard side SB each comprise side wall sections 18, 28running in a flat arcuate manner and extending from the nose strips 11,21 in the direction of the end strip 15, having a length L2 whichextends over the length L′2 of the side wall section 18 from the nosestrips 11, 21 as far as the greatest profile thickness PD plus a lengthL″2 which corresponds to at least ⅓ of the length L′2, wherein the sidewall section 28 running in a flat arcuate manner is adjoined by therectilinearly running side wall section 16 which ends in the end strip15 (FIG. 5).

Furthermore, the upper rudder blade section 10 on the port side BB andthe lower rudder blade section 20 on the starboard side SB each comprisea highly curved side wall section 19, 29 running in an arcuate mannerand extending from the nose strips 11, 21 in the direction of the endstrip 15, having a length L3 which extends over the length L′3 of theside wall section 19 from the nose strips 11, 21 as far as the greatestprofile thickness PD plus a length L″3 which corresponds to at least ⅓of the length L′3. The highly curved side wall section 19, 29 running inan arcuate manner is adjoined by the rectilinearly running side wallsection 17, 27 which ends in the end strip (FIG. 5, 4D).

As a result of this configuration of the two rudder blade sections 10,20, the side wall sections on both sides have ascending profiles fromthe nose strips 11, 21 and from the end strip 15 in the direction of thelargest profile thickness PD.

The nose strip 11 of the upper rudder blade section 10 and the nosestrip 21 of the lower rudder blade section 20 are laterally offset toport BB and starboard SB with respect to the longitudinal central lineLML in such a manner that the central line M2 drawn through thelaterally offset nose strip sections is running at an angle α of atleast 30 to 100 but also higher, preferably 8° to the longitudinalcentral line LML of the cross-sectional area of a rib.

The rudder arrangement 200 further comprises a rudder post 140, inparticular made of forged steel or another suitable material, whichcooperates functionally with the rudder blade 100, which is mounted in arudder pipe 120, in particular made of forged steel or another suitablematerial, by means of at least one bearing 150. The rudder post 140 isarranged in the area of the greatest profile thickness PD of the upperrudder blade section 10 and only therein (FIGS. 1, 2, 3 and 15), i.e. atthe point of intersection of the line representing the greatest profilethickness PD and the longitudinal central line LML (FIG. 5). The rudderpost 140 extends together with its fastening device 145 over the totalheight of the upper rudder blade section 10 of the rudder blade 100. Forconstruction reasons the rudder pipe 120 with the rudder post 140 canalso be arranged in the upper rudder blade section 10 between thegreatest profile thickness PD and the nose strips 11, 21.

The rudder pipe 120 which is drawn deeply into the upper rudder bladesection 10 as a cantilever is provided with an inner hole 125 forreceiving the rudder post 140 (FIG. 14). The rudder pipe 120 is arrangedby inserting the rudder pipe into gaps 105 in the frames 40 of the upperrudder blade section 10 according to the outside diameter of the rudderpipe (FIGS. 3, 8, 8A, 8B, 8C).

The rudder pipe 120 as a cantilever is provided with a central innerlongitudinal hole 125 for receiving the rudder post 140 for the rudderblade 100. In addition, the rudder pipe 120 as far as the rudder blade100 connected to the rudder post end is configured as extending onlyinto the upper rudder blade section 10. In its inner hole 125 the rudderpipe 120 has the bearing 150 for mounting the rudder post 140, thisbearing 150 preferably being arranged in the lower end region 120 b ofthe rudder pipe 120. The end 140 b of the rudder post 140 is guided outfrom the rudder pipe 120 with a section 145. The free lower end of thislengthened section 145 of the rudder post 140 is firmly connected to theupper rudder blade section 10 at 170, wherein here however, a connectionis provided which makes it possible to release the rudder blade 100 fromthe rudder post 140 if, for example, the propeller shaft needs to beexchanged. The connection of the rudder post 140 in the area 170 withthe twisted rudder blade 100 in this case lies above the propeller axisPA so that for dismantling the propeller shaft the rudder blade 100 onlyneeds to be removed from the rudder post 140 so that it is not necessaryto withdraw the rudder post 140 from the rudder pipe 120 to exchange apropeller axle since both the free lower end 120 b of the rudder pipeand also the free lower end of the rudder post 140 lie above the middleof the propeller shaft. In the embodiment shown in FIG. 15 only a singleinner bearing 150 is provided for mounting the rudder post 140 in therudder pipe 120; another bearing for the rudder blade 100 on the outerwall of the rudder pipe 120 can be omitted.

The rudder blade 100 is provided with a retraction or recess indicatedat 160 for receiving the free lower end 120 b of the rudder pipe 120.

The cross-section of the rudder pipe 120 is designed as thin-walledhaving at least one collar bearing 130 on its inner wall side in thearea of its free end for mounting the rudder post 140. Additionalbearings for the rudder post can also be provided at other positions ofthe rudder pipe 120. In its end region 140 b the rudder post 140 isguided out of the rudder pipe 120 with a section 140 a and the end ofthis section 140 a is connected to the upper rudder blade section 10(FIG. 14).

According to FIGS. 3 and 7, the upper rudder blade section 10 and thelower rudder blade section 20 consist of a rudder plating forming theside walls and horizontal web plates or frames 40, 50 and vertical webplates or frames which form the inner stiffening of the two rudderblades. The web plates are provided with lightening and limber holes.

As shown in FIGS. 3, 4, 4A, 4B, 4C and 8, 8A, 8B, 8C, all the frames 40of the upper rudder blade section 10 of the rudder blade 100 have thesame shape, the same side wall guidance and matching nose strip 11 andend strips 15, the length of the frames decreasing from the respectivelyuppermost frame to the lowermost frame and thus the size of thecross-sectional surfaces of the frames decreasing from top to bottom, sothat the nose strips 11 run obliquely towards the base of the rudderblade 100 (FIG. 1).

All the frames 50 of the lower rudder blade section 20 have the sameshape, the same side wall guidance and matching nose strip 21 and endstrips 15, the length of the frames 50 decreasing from the respectivelyuppermost frame to the lowermost frame and thus the size of thecross-sectional surfaces of the frames decreasing from top to bottom, sothat the nose strips 11 run obliquely towards the base of the rudderblade 20.

As a result of this configuration, the nose strips 11, 21 of the upperrudder blade section 10 and the lower rudder blade section 20 runobliquely downwards, whereas the end strips 15 run rectilinearly andparallel to the longitudinal axis of the rudder post 140, as shown inFIG. 1.

The two rudder blade sections 10, 20 can be connected directly to oneanother. In FIGS. 7 and 11, the two rudder blade sections 10, 20 areconnected to one another by means of a fastening plate 45. Thisfastening plate 45 has symmetrical cross-sectional surface sections 46,47 on both sides of the longitudinal central line LML and a surfaceprofile and dimensions which enclose the base plate 42 of the upperrudder blade section 10 and the cover plate 41 of the lower rudder bladesection 20 with their profiles and dimensions so that when the upperrudder blade profile 10 is placed one on top of the other on thefastening plate 45 and the lower rudder blade section 20 is placed onthe fastening plate 45 from below, this projects laterally with a verysmall edge region from the rudder blade sections 10, 20 placed one uponthe other (FIGS. 10 and 11). The fastening plate 45 has a semicircularedge rounding 11′ lying on the central longitudinal line LML, facing thepropeller and an edge 15′ facing away from the propeller, which goesover into the end strips 15 of the two rudder blade sections 10, 20. Theside wall surfaces 45 a, 45 b of the fastening plate 45 have matchingarc profiles.

As shown in FIGS. 3 and 10, the lower rudder blade section 20 adjoinsthe fastening plate 45 in the lower region, its frames 50 having across-sectional surface configuration and shape which corresponds tothat of the frames 40 but with the frame 40 turned through 90° about itscentral longitudinal line LML (FIGS. 4D, 4E, 8D, 8E, 8F).

According to FIGS. 7, 8, 8A, 8B and 8C, the frames 40 of the sections A,B, C and D are the same in terms of profile but the cross-sectionalsurface of the individual frames 40 decreases from top to bottom so thatthe nose strip 11 runs obliquely. Section C is adjoined by section Dwith the fastening plate 45. The frames 50 of sections E, F and G of thelower rudder blade section 20 have the same profiles as the profiles ofthe frames 40 but the side walls with the highly curved arcuate sidewall sections 29 of the frames 50 lies on the port side BB (FIGS. 8D, 8Eand 8F) whereas in the exemplary embodiment of FIG. 7, the side walls ofthe frames 40 with the highly curved arcuate side wall sections 19 lieon the starboard side SB (FIGS. 8, 8A, 8B and 8C). The cross-sectionalsurfaces of the frames 50 of the lower rudder blade section 20 decreasefrom top to bottom in relation to their length so that the nose strip 21of the lower rudder blade section 20 also runs obliquely (FIG. 7).

FIG. 9 shows the upper cover plate 43 of the upper rudder blade section10 which is provided with the gap 105 for introducing the rudder pipe120. FIG. 10 shows a view from below of the rudder blade 100 with itstwo rudder blade sections 10, 20 and the frames 40 and 50.

The diameter of the gap 105 or hole in the upper rudder blade section 10for receiving the rudder pipe 120 for the rudder post 140 is somewhatsmaller than the largest profile thickness PD of the rudder bladesection 10. As a result of this configuration a very slender rudderblade profile is created.

The configuration and the cross-sectional profile of the rudder blade100 with its two rudder blade sections 10, 20 are such that the flatlycurved arcuate side wall sections 18, 28 of the upper and lower rudderblade sections 10, 20 have a short length L2, L′2 compared with thelength L3 of the highly curved arcuate side wall sections 19, 29 of theupper and lower rudder blade sections 10, 20 (FIGS. 5 and 6). Thedistance α of the side wall section 18 of the upper rudder blade section10 to the longitudinal central line LML and the distance α1 of the sidewall section 19 are the same. As far as the end strip 15 the distancesα, α1 are always the same but they decrease in the direction of the endstrip 15. The following distance relationships are obtained in thedirection of the nose strip 11:

α2<α3

α4<α5

α6<α7

The greatest profile thickness PD then follows. The following distancerelationships are then obtained in the direction of the nose strip

α8>α9

α10>α11

α12>α13

α14>α15

α16>α17

α18>α19,

wherein the ratio of the distances α16 to α17 is about 2:1. FIG. 6clearly shows the ratio of the distances to one another, i.e. that thedistances α9, α11, α13, α15, α17, α19 decrease substantially withrespect to the distances α8, α10, α12, α14, α16, α18 in the direction ofthe nose strip 11. This cross-sectional profile with the distances shownextends through all the cross-sections of the upper rudder blade section10 and through all the cross-sections of the lower rudder blade sinceall the cross-sectional surfaces of the upper rudder blade section 10have the same shapes, which also applies to the cross-sectional surfaceof the lower rudder blade section 20 and specifically taking intoaccount the fact that the cross-sectional surface or frames of therudder blade 100 taper from top to bottom in relation to their lengthsand in relation to their regions facing the nose strips (FIG. 10).

According to a further embodiment according to FIG. 14, the arc lengthBL1 of the highly curved arcuate side wall sections 19, 29 of the upperand lower rudder blade section 10, is greater than the arc length BL ofthe flatly curved arcuate side wall sections 18, 28 of the upper andlower rudder blade section 10, 20 so that the transition zones ÜB1 ofthe highly curved arcuate side wall sections 19, 29 of the upper andlower rudder blade sections 10, 20 to the side wall sections 17, 27running rectilinearly to the end strip 15 and the transition zones ÜB ofthe flatly curved arcuate side wall sections 18, 28 of the upper andlower rudder blade sections 10, 20 to the side wall sections 16, 26running rectilinearly to the end strip 15 are offset in the direction ofthe end strip 15 in such a manner that the transition zone ÜB1 withrespect to the transition zone ÜB is facing the end strip. In this case,the lengths of the side wall sections 18, 19 and 28, 29 are as follows:

L3≧L2

L′2<L′3

L4>L′4

(FIG. 14).

The legs of the rectilinear side wall sections 16, 17, 26, 27 of theupper rudder blade section 10 and the lower rudder blade section 20which converge to the end strip 15, preferably have the same lengths butan unequal length configuration is also possible.

The invention also embraces rudder arrangements in which the twistedrudder blade 100 is provided with a fin extending over the two rudderblade sections 10, 20.

The rudder arrangement according to the invention is characterised bythe features specified in the claims, by the embodiments presented inthe description and by the exemplary embodiments shown in the figures ofthe drawings.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the inventive principles, it will beunderstood that the invention may be embodied otherwise withoutdeparting from such principles.

1. A rudder arrangement for ships having higher speeds comprising acavitation-reducing twisted, in particular balanced rudder, comprising arudder blade with a propeller (115) arranged on a drivable propelleraxis (PA), which is associated with the rudder blade, and a rudder post(140) connected to the rudder blade (100), wherein the rudderarrangement (200) a.) comprises of a balanced rudder blade (100)preferably having a slender profile with a small profile thickness,comprising two superposed rudder blade sections (10, 20) having the sameor different heights, preferably comprising a lower rudder blade section(20) having a smaller height compared with the height of the upperrudder blade section (10) and comprising nose strips (11, 21) facing thepropeller (115), having an approximately semicircular profile, which arepositioned in such a manner that one nose strip (11) is offset to port(BB) or starboard (SB) and the other nose strip (21) is laterally offsetto starboard (SB) or port (BB) with respect to the longitudinal centralline (LML) of the rudder blade (100), wherein the side wall surfaces(12, 13; 22, 23) of the two rudder blade sections (10, 20) converge intoan end strip (15) facing away from the propeller (115), a1.) wherein thetwo nose strips (11, 21) and the end strip (15) run downwards in aconically tapering manner accompanied by a reduction in thecross-sectional areas (30) from the upper region (OB) to the lowerregion (UB) of the rudder blade (100), a2.) or the end strip (15) runsrectilinearly and parallel to the rudder post (140) and the two nosestrips (11, 21) run downwards in a conically tapering manner accompaniedby a reduction in the cross-sectional areas (30) from the upper region(OB) to the lower region (UB), a3.) wherein the cross-sectional surfacesections (31) of the upper rudder blade section (10) and the lowerrudder blade section (20) in the region between the end strip (15) andthe greatest profile thickness (PD) of the rudder blade (100) have alength (L), which is equal to at least 1½ times the length (L1) of thecross-sectional surface sections (32) of the upper rudder blade section(10) and the lower rudder blade section (20) between the greatestprofile thickness (PD) of the rudder blade (100) and the nose strips(11, 21), a4.) wherein the upper rudder blade section (10) on the portside (BB) and the lower rudder blade section (20) on the starboard side(SB) each comprise a side wall section (18, 28) running in a flatarcuate manner and extending from the nose strips (11, 21) in thedirection of the end strip (15), having a length (L2) which extends overthe length (L′2) of the side wall sections (18) from the nose strips(11, 21) as far as the greatest profile thickness (PD) plus a length(L″2) which corresponds to at least ⅓ of the length (L′2), wherein theside wall section (18, 28) running in a flat arcuate manner is adjoinedby the rectilinearly running side wall section (16, 26) which runs outin the end strip (15), a5.) wherein the upper rudder blade section (10)on the port side (BB) and the lower rudder blade section (20) on thestarboard side (SB) each comprise a highly curved side wall section (19,29) running in an arcuate manner and extending from the nose strips (11,21) in the direction of the end strip (15), having a length (L3) whichextends over the length (L′3) of the side wall sections (19) from thenose strips (11, 21) as far as the greatest profile thickness (PD) plusa length (L″3) which corresponds to at least ⅓ of the length (L′3),wherein the highly curved side wall section (19, 29) running in anarcuate manner is adjoined by the rectilinearly running side wallsection (17, 27) which runs out in the end strip (15), a6.) wherein thetwo rectilinearly running side wall sections (16; 17; 26, 27) have thesame lengths in pairs and the cross-sectional surface sections locatedbetween the two side wall sections (16, 17; 26, 27) are the same sizeand are configured symmetrically and a7.) wherein the distance betweenthe side wall section (18; 28) running in a flat arcuate manner from thelongitudinal central line (LML) is greater than the distance between thehighly arcuately running side wall section (19; 29) from thelongitudinal central line (LML) and the cross-sectional surface sectionslocated between the two side wall sections (18; 28) running in a flatarcuate manner on both sides of the longitudinal central line (LML) areconfigured asymmetrically and is b.) comprised of a rudder post (140)cooperating functionally with the rudder blade (100), having at leastone bearing, b1.) wherein the rudder post (140), in particular made offorged steel or another suitable material, together with the rudder pipe(120) receiving said post, in particular made of forged steel or anothersuitable material is arranged in the area of the greatest profilethickness (PD) or between this and the nose strips of the upper rudderblade section (10) therein and extends with its end fastening device(145) over the entire height of the upper rudder blade section (10),b2.) wherein the rudder pipe (120) for the rudder post (140) which isdrawn deeply into the upper rudder blade section (10) as a cantilever isprovided with a central longitudinal hole (125) for receiving the rudderpost (140), b3.) wherein the rudder pipe cross-section is designed asthin-walled and the rudder pipe (120) preferably has a collar bearing(130) on the inner wall side in the area of its free end for mountingthe rudder post (140), and b4.) wherein in an end region (140 b) thereofrudder post (140) is guided out from the rudder pipe (120) with asection (140 a) and the end of this section (140 a) is connected to theupper rudder blade section (10).
 2. The rudder blade arrangementaccording to claim 1, wherein a fastening plate (45) is arranged betweenthe upper rudder blade section (10) and the lower rudder blade section(20) and is firmly connected to the rudder blade sections (10, 20),wherein the fastening plate (45) has symmetrical cross-sectional surfacesections (46, 47) on both sides of the longitudinal central line (LML)and a surface profile and dimensions which enclose the base plate (42)of the upper rudder blade section (10) and the cover plate (41) of thelower rudder blade section (20) with their profiles and dimensions. 3.The rudder arrangement according to claim 1, wherein the nose strip (11)of the upper rudder blade section (10) and the nose strip (21) of thelower rudder blade section (20) are laterally offset to port (BB) andstarboard (SB) with respect to the longitudinal central line (LML) insuch a manner that the central line (M2) drawn through the laterallyoffset nose strip sections is running at an angle α of at least 3° to10° but also higher, preferably 8° to the longitudinal central line(LML) of the cross-sectional area of a rib.
 4. The rudder arrangementaccording to claim 1, wherein the flatly curved arcuate side wallsections (18, 28) of the upper and lower rudder blade sections (10, 20)located on the port side (BB) and the starboard side (SB) have a shorterlength (L4) compared with the length (L5) of the highly curved arcuateside wall sections (19, 29) of the upper and lower rudder blade sections(10, 20) located on the starboard side (SB) and on the port side (BB).5. The rudder arrangement according to claim 1, wherein the arc length(BL1) of the highly curved arcuate side wall sections (19, 29) of theupper and lower rudder blade sections (10, 20) is greater than the arclength (BL) of the flatly curved arcuate side wall sections (18, 28) ofthe upper and lower rudder blade sections (10, 20) so that thetransition zones (ÜB1) of the highly curved arcuate side wall sections(19, 29) of the upper and lower rudder blade sections (10, 20) to theside wall sections (17, 27) running rectilinearly to the end strip (15)and the transition zones (ÜB) of the flatly curved arcuate side wallsections (18, 28) of the upper and lower rudder blade sections (10, 20)to the side wall sections (16, 26) running rectilinearly to the endstrip (15) are offset in the direction of the end strip.
 6. The rudderarrangement according to claim 1, wherein the diameter of the gap (105)or hole in the upper rudder blade section (10) for receiving the rudderpipe (120) is somewhat smaller compared with the greatest profilethickness (PD) of the rudder blade section (10).
 7. The rudderarrangement according to claim 1, wherein the edge or nose strip (11,21) of the rudder blade (100) facing the propeller (115) runs obliquelyto the edge or end strip (15) facing away from the propeller (115) at anangle β of at least 5°.
 8. The rudder arrangement according to claim 7,wherein the angle β is 10°.